It's highly recommended that you keep both pg_dump backups and, if up-to-date backups or warm standby are important, continuous archiving backups. The former can protect you against damage caused by undetected disk or file system corruption, severe admin errors, PostgreSQL bugs (gasp!), etc. The latter can make sure that you have backups up to the minute of a failure in most cases, rather than having to go back to last night's tapes.